Problem: $ { \left[\begin{array}{rrr}{0} & {1} & {-2} \\ {3} & {1} & {2}\end{array}\right]+\left[\begin{array}{rrr}{4} & {0} & {0} \\ {2} & {0} & {3}\end{array}\right] = {?} } $
Explanation: To find the sum of two matrices, add the corresponding items between each matrix. ${\left[\begin{array}{rrr}{0}+{4} & {1}+{0} & {-2}+{0} \\ {3}+{2} & {1}+{0} & {2}+{3}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{rrr}{4} & {1} & {-2} \\ {5} & {1} & {5}\end{array}\right]}$